The importance of mosquitoes in the transmission of malaria, yellow fever, dengue, encephalitis, and filariasis is well known. Since the etiological agents of all these diseases, protozoans, viruses, and nematode worms, as well as the bacteria and fungi often harbored by mosquitoes, are ingested by the insects before transmission can occur, they are obviously concerned with the digestive systems of their hosts. Extensive physiological investigations of the culicid digestive system may be expected to provide fundamental bearing on the relationships which mosquitoes have with these several disease-producing agents. Data from such research would not only add to the store of our knowledge but might conceivably be utilized in several practical ways also, such as: (a) devising a means of interrupting the development of the microorganism or virus within the mosquito, thus breaking the transmission cycle2; (b) repelling or destroying the mosquito itself as a result of better understanding its feeding and digestive processes3; or (c) assisting in the development of procedures for culturing these agents outside the mosquito.4